Ensure interface extends valid expr.

javascript/extractor/src/com/semmle/js/ast/MemberExpression.java

@@ -69,4 +69,9 @@ public class MemberExpression extends Expression
   public void setSymbol(int symbol) {
     this.symbol = symbol;
   }
+
+  @Override 
+  public boolean isValidExpression() {
+    return object instanceof ITypeExpression || object instanceof DynamicImport;
+  }
 }

javascript/extractor/src/com/semmle/ts/ast/ITypeExpression.java

@@ -10,4 +10,6 @@ import com.semmle.js.ast.Literal;
  * however, some expressions such as {@link Literal} type may occur in a type annotation because the
  * TypeScript AST does not distinguish <code>null</code> literals from the <code>null</code> type.
  */
-public interface ITypeExpression extends INode, ITypedAstNode {}
+public interface ITypeExpression extends INode, ITypedAstNode {
+    public default boolean isValidExpression() { return true; }
+}

javascript/extractor/src/com/semmle/ts/extractor/TypeScriptASTConverter.java

@@ -1907,7 +1907,7 @@ public class TypeScriptASTConverter {
   }
 
   private ITypeExpression asType(Node node) {
-    return node instanceof ITypeExpression ? (ITypeExpression) node : null;
+    return node instanceof ITypeExpression && ((ITypeExpression)node).isValidExpression() ? (ITypeExpression) node : null;
   }
 
   private List<ITypeExpression> convertChildrenAsTypes(JsonObject node, String child)